Ready, Set, Glow

Thursday, March 19, 2015

by Lincoln Park Zoo

in

Chicago Wildlife Watch

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Camera traps are incredibly useful and can allow researchers to collect large amounts of data on where species are located through space and time. However, at times it can be difficult, if not downright impossible, for citizen scientists to classify some of the photos these devices capture.

Sadly, the cameras do not increase how “cooperative” Chicago’s raccoons, coyotes and opossums can be with regard to “striking a pose” before going on their merry way. At times, all you see in a photo is a blurred blob, a “floating” tail at the edge or a pair of “glowing” eyes attached to what you can only assume is the vague outline of an animal. Here, we provide some more tips on better identifying blobs, tails and eye shine so you can classify those confusing not-so-closeups with confidence!

Sometimes it is hard to identify “blurs.” What do you think it is?

With blurred photos our best suggestion is to try and determine the size or shape of the animal and make an educated guess from that. Can you make out a long tail? Maybe it’s a coyote. If you are wrong, it’s okay! UWI researchers will flag and ID photos that don’t have consensus. “Floating” tails—seen in images where the animal has walked mostly out of the field of the camera—are a bit easier. If you spend a bit of time looking at the tails of our urban species—be it on Chicago Wildlife Watch or elsewhere on the web—you can get pretty good at it.

The most difficult photos to ID are those with only glowing eyes. But before we provide some tips on how to ID these photos, consider this question: do you know where eye shine comes from? The reason mammals’ eyes “glow” at night is that the lenses in their eyes act like a mirror and reflect some of the available light. Because we use infrared cameras the IR waves and visible light bounce off mammalian eyes and a “glow” is captured in the pictures. Some field researchers use the reflective capacity of eyes to their advantage and will scan areas with flashlights to look for eye shine! So now that we know why some animals’ eyes shine, let’s focus on how to differentiate and identify species based on their eye shine.

Although it’s sometimes difficult to discern the shape of an animal, you can deduce the species by paying close attention to the location of the eyes in the picture. If the eyes are up in a tree branch, in a bush or very close to the ground you can use the process of elimination to remove some species from the list of possibilities. Furthermore, the shape and size of the eyes and distance between them also provide hints. Below, we provide some species-specific explanations and photos of the more common Chicago critters you will encounter on Chicago Wildlife Watch.

Mice and Rats

While it is practically impossible to ID the specific species of mouse or rat in a camera-trap photo, these groups have the smallest and closest eyes, which makes it relatively easy to identify them. Given their small size, you almost always see these tiny white “dots” near the ground. Even when the body looks like a “dark blob” you should compare the eye size relative to the body in order to identify the animal. For mice you generally see one eye on a clementine-size “blob”. Rats, on the other hand, have a greater body mass relative to the size of their small eyes. They are the size of an eggplant and you can often see both small eyes as it runs away. A key feature of both mice and rats is their cord-like tail. Think computer cord for rat tails and headphone cord for mouse tails. Remember, when in doubt, you can always zoom in to get a better view of the body and the tail.

The side view of a mouse.

Notice the cord-like tail of the rat.

Opossum

Like mice and rats, opossums tend to stay low to the ground, although sometimes they are found climbing trees. Their eyes glow brighter than rats and mice and are close together on the front of the face. Key features of an opossum are its pointed white snout and rat-like tail. Even in pictures taken at night opossum fur is easily defined by the blotchy gray and white coloration. Think you see an extra set of “eyes” on the body of an opossum? Yes! What you are probably seeing are the eyes of a baby opossum being carried on its mother’s back or in a pouch on her abdomen.

Notice the pointed, white face of the opossum.

Mama opossum with three babies.

Skunks

Skunks are very easy to identify. Their tiny, glowing eyes and black and white fur easily distinguishes this species from all the other animals we capture on camera.

The black and white coloration of the skunk is easy to identify even in the dark.

Raccoons

Raccoons are dexterous climbers and can be found in trees, on the ground or hidden in bushes. Their eyes are further apart than on opossums, and their face is often higher up from the ground. Their eyes are larger than those of mice, rats and opossum. Look closely for a dark band around the eyes as that can be a good indication the eyes belong to a raccoon and not an opossum.

Notice the raccoon’s eyes are lower than its hunched back.

Deer

Deer have the largest and roundest eyes on Chicago Wildlife Watch. As the tallest animal in Chicago, deer are easy to identify because their eyes are very far from the ground and are located on the sides of their head. Additionally, deer tend to be very curious and often stare right into the camera!

Deer looking to the left.

Rabbits

Eye placement on rabbits is similar to deer. Their eyes tend to be more on the sides of the head than towards the front as on opossums or raccoons. As such, if you only see a single, glowing eye close to the ground it most likely belongs to this little lagomorph. Even if the picture has caught the animal in mid-movement, look for this species’ large ears to identify it.

A rabbit jumping to the right.

Foxes and Coyotes

It is actually pretty difficult to tell these two apart from just eye glow. However, there are a few features to look for. The location of the eyes can help you identify which species is in the photo. Red and gray foxes are smaller—about 1 foot tall—while coyotes stand about 2 feet tall. Furthermore, red foxes’ eyes are slightly closer together and tend to glow more brightly than coyotes’ eyes. If you can make out additional features remember that an elongated and lighter muzzle indicate coyote while foxes have black ears, black “boots” and a white tail. Gray foxes are very uncommon and therefore not covered in this post. Check out our previous post, Chicago Canine Close-Up.

You can see the bright eye glow of the red fox.

Coyote looking through the branches.

Squirrels

Though grey squirrels and fox squirrels are most active during the day, we still get some night-time photos. By paying close attention to the bushy tail one can easily identify a squirrel, but it’s hard to narrow it down to a particular species. Do your best to look for the “halo” around the tail as grey squirrels can still be identified this way in black and white photographs. Flying squirrels, on the other hand, are much more rare and nocturnal. Despite this, they are easy to identify. You can tell flying squirrels apart from other species due to their large round eyes and skin flaps on the sides of their bodies. Finally, they are most often in trees!

Even in the dark the gray squirrel “halo” on the tail is still visible.

Flying squirrel climbing on a tree. The arrow points to the skin flap between the front and back of the leg.

Learn More

Heads Up on Local Wildlife
Zoo biologist Liza Watson Lehrer explains how an animal’s head posture reflects its sense of risks in its environment.

Field Work in the City
Cities may not be pristine landscapes, but plenty of animals thrive in urban settings, biologist Mason Fidino shares. See how zoo scientists are using more than 120 motion-triggered cameras to monitor local wildlife from the Loop to the burbs.